The adult E. multilocularis (1.2 to 3.7 mm)resides in the small bowel of the definitive hosts, which are foxes and, to a lesser extent, dogs, cats, coyotes, and wolves. Gravid proglottids (bisexual reproductive segments) release eggs that are passed in the feces. After ingestion by a suitable intermediate host (a small rodent), the egg hatches in the small bowel and releases an oncosphere that penetrates the intestinal wall and migrates through the circulatory system into the liver, where larval growth remains indefinitely in the proliferative stage, resulting in invasion of the surrounding tissues.